1. Field of the Invention
The invention lies in the field of electronic communications. The invention relates to a reduced order model location method for multi-hop networks.
2. Description of the Related Art
In a multi-hop sensor network, because of limited transmitted power, a communications node can only communicate with a small subset of the other communications nodes in the entire network. A traditional location system may not work for a multi-hop network because the multi-hop network requires that any node be linked directly to three reference nodes with known locations that are not on a line in a two-dimensional space or to four reference nodes with known locations that are not on a plane in a three-dimensional space. The consequence of such failure is that many nodes will not be able to locate, especially when the sensor network is sparse.
An iterative or successive procedure is used to change a node to an induced reference node if the node can be located using the traditional approach. Thus, induced reference nodes are nodes that initially do not know their coordinates but, because they have the range measurements from a sufficient number of nodes with known coordinates, they can solve a simple triangulation problem and discover their own coordinates. See “Recursive Position Estimation in Sensor Networks,” Joe Albowicz, Alvin Chen, and Lixia Zhang, UCLA Research Laboratory, 2001. However, after such a procedure, there will still be a subset of the nodes that is not located, especially in a sparse sensor environment. Moreover, existing methods that decide if a node is locatable or not do so by establishing the number of independent paths of each node to reference nodes, which becomes highly computationally intense for large networks. This method can also be shown to result in erroneous decisions as far as position solutions are concerned.